Overload relay



Feb. 9, 1932.

G. O. WHLMS OVERLOAD RELAY Filed Aug. 8, 1928 33 V 3 xv J MP will Patented Feb. 9, 1932 UNITED STATES PATENT OFFICE GUSTAV O. WILMS, OF MILWAUKEE, WISCONSIN, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO ALLEN-BRADLEY COMPANY, OF WISCONSIN MILWAUKEE, WISCONSIN, A CORPORATION OF OVER-LOAD RELAY Application filed August 8, 1928. Serial No. 298,801.

This invention relates particularly to overload relays of the thermally actuated type.

Heretofore, thermally actuated overload relays have necessitated manual resetting of the relay after each occurrence of an overload in the circuit with which it is used and this invention contemplates as an object the provision of means incorporated in an overload relay for automatically resetting the relay after each occurrence of an overload.

Another'object of this invention resides in the provision of a thermally actuated member which operates the relay upon the occurrence of an overload and which also functions to return the parts to their normal position to reset the relay.

And a more specific object of this invention resides in the provision of a bi-metallic member so arranged asto store energy within itself upon the application of heat caused by an overload to quickly operate the relay the instant it is released and which, as it cools, returns the parts to their normal position to automatically reset the device.

With the above and other objects in view which will appear as the description proceeds, my invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

In the accompanying drawings, I have illustrated one complete example of the physical embodiment of my invention constructed according to the best mode I have so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a top plan view of an overload relay embodying my invention;

Figure 2 is an end view with parts broken away and in section to more clearly illustrate structural details, and

Figure 3 is a plan View similar to Figure 1 illustrating the position of the parts after the relay has functioned upon occurrence of an overload.

1 Referring now more particularly to the accompanying drawings, in which like numer- 7 frame 6 secured to the panel by bolts or other securing means 7 The major portion 8"of the frame is positioned horizontally and has a leg 9 extending downwardly therefrom through which the fastenings 7 pass to secure the frame to the panel. second leg 10 is also extended downwardly from the frame part 8, the plane of the leg 10 being substantially at right angles with respect to the plane of the leg 9.

A threaded aperture 11 extends through the major portion 8 of the frame to receive a bushing 12 formed of suitable insulating and heat resisting material, the space between the threads of the bushing 12 and the aperture 11 being filled with a cement 13 which also extends conically from the upper outer periphery of the bushing 12 to the adjacent face of the frame to secure the bushing in the aperture. Fixed in the opening 14 of bushing 12 and secured therein with its ends projecting upwardly and downwardly bycement 13' is a stem 15 having a heating element positioned on that portion thereof extending below the part 8 of the frame, the heating element 16 consisting of a spool 17 encircled by a band of resistance material 18 secured thereon by cement or othenmeans 19, the ends 20 and 21 of the resistance material being electrically connected with conductors 22 and 23, respectively, by which the heating element is connected in a circuit, not shown, through brackets 24 and 25. The inner ends of the brackets are secured to the panel 5 and the outer ends thereof have the ends 20 and 21 of the resistance material 18 connected therewith by screws 26.

A substantially cup-shaped member 27 is fixed to the stem 15 at a point directly above bushing to the face of the frame continues upwardly to the outer-periphery of the member '27 to asslst in securing the stem to the insulating bushing. The cup-shaped member 27 receives the lower end 28 of a tubular mount pin 34. The arm ing member 29 positioned on the upper outer end of the stem 15, the bore of which is spaced from the stem and the space therebetween being filled with solder 30 or other material having arelatively low melting point. The solder also substantially Surrounds the lower end 28 of the mounting member within the cup-shaped member 27 to fix the mounting member on the stem.

An actuating member 31 is secured to the outer end of the mounting member 29 and has an arm 32 extended therefrom on the outer end of which a roller 33 formed of insulating material is revolvably mounted by a 32 carrying the roller 33 is normally positioned so that the periphery of the roller is slightly spaced from a switch member 35 formed of spring metal and having one end bent back on itself to be secured to the panel tor 37 is electrically connected. The outer free end of the switch member 35 carries a contact 38 which normally engages a stationary contact 39 mounted on the panel by a bolt 40 through which it is electrically connected with a conductor 41; the conductors 41 and 37 being thus bridged through the switch member 35.

Extended angularly from the actuating member 31, with respect to the arm 32, is a second arm 42, the outer end of which is directed downwardly, of a bi-metallic member 44 connected therewith by a bolt 45. The bi-metallic member 44 is looped around the heating element 16 and hasits metal of greatest expansion on the inside, its other end being secured to the stationary leg 10 depending downwardly from the bracket 6 by a bolt 46.

Upon the occurrence of an overload in the circuit connected with the conductors 22 and 23, an lncreased current passes through the heating element which raises its temperature and the bi-metallic member 44 due to its close proximity to the heating element is thus affected, tending to straighten and produce r0 tation of the actuating member 31 in a counter-clockwise direction. The tendency of the bi-metallic member 44 to cause the actuating member 31 to rotate, however, has no effect on the actuating member until the heat produced by the heating element 16 increases to a point at which the solder 30 melts and releases the actuating member. At this time, sulficient energy has been stored up in the bimetallic member to quickly move the actuating member to engage its roller 33 with the switch member 35 and disengage its contact 38 from the stationary contact 39 with a snap to rupture the circuit in which the conductors 41 and 37 'are'included.

The rupturing of the circuit by the switch member 35 also opens the circuit of the heat ing coil permitting the heating element and the bi-metallic member to cool. The bi-me 5 by a bolt 36-with which a conduc as at 43, to have one end tallic member 44 in cooling assumes its normal position and retracts the actuating member to its inoperative position and inasmuch as no voltage is being impressed upon the conductors 41 and 37 the slow closing of the switch 35 has no injurious effects and the movement of the bi-metallic member 44 is so timed that the actuating member assumes its normal inoperative position before the solder 30 sets to secure it to the stationary stem 15. 1

From the foregoing description taken in connection with the accompanying drawings it will be readily apparent to those skilled in the art to which an invention of this character appertains that I provide an overload relay having means for quickly rupturing a circuit and in which said means also functions to reset the relay after the occurrence of an overload.

I claim:

1. In an over-load relay, a switch member normally yieldably held in one position, an actuating member operable to move the switch member out of its normal position,

athermal element adapted to move the actuating member upon a change in temperature at the thermal element, means for heating the element, and therm'ally responsive means normally holding the actuating member against the action of the thermal element, whereby rising temperature at the thermal element stores up energy in the element until the temperature at the thermally responsive means reaches a predetermined degree at' which the actuating member is released to be quickly moved by the stored up energy in the thermal element to move the switch member out of its normal position with a snap.

2. In an over-load relay, a switch normally urged to one 1position, thermally actuated means for quic ly moving the switch to another position upon the occurrence of a predetermined condition, thermally responsive means opposing the movement of the ther-- mally actuated means until a predetermined time during the occurrence of said condition, said thermally responsive means having, a constant fusion point, and the thermally actuated means moving to its inoperative po-' sition after theoccurrence of said predetermined condition to permit the urging means of the switch to move it to its first position.

3. In an overload relay, a switch normally yieldably urged to one position, thermally actuated means for quickly moving the switch to another position upon the occurrence of a predetermined condition, means for opposing the movement of the thermally actuated means until a predetermined time during-the occurrence of said condition, said means including a soldered joint which melts upon the occurrence of said predetermined condition, and the thermally actuated ineans moving to its inoperative position after the occurrence of said predetermined condition to permit the urging means of the switch to move the same to its first position before the soldered joint resets itself.

4. In an over-load relay, a switch normally yieldably urged to one position, a member operable to move the switch to its other position, thermally actuated means adapted to store up energy within itself upon the occurrence of predetermined condition to move the member and quickly move the switch to said other position, and fusible means holding the thermally actuated means against movement until a predetermined time during the occurrence of said condition, said fusible means having a constant fusion point and the thermally actuated means moving to its inoperative position after the occurrence of said predetermined condition to permit the switch to return to its first position.

5. In an overload relay having aheating element and a switch normally urged to closed position, a member movable about an 2 axis of the heating element to open the switch,

and thermally actuated means adapted to store up energy within itself upon heating of the heating element to move the member about said axis and quickly open the switch.

6. In an overload'relay including a heating element and a switch normally yieldably urged to closed position, an actuating member operable to open the switch, means releasably securing the actuating member in fixed position, and a thermally actuated member adapted upon heating of the element to store up energy within itself to quickly move the actuating member to open the iwitch upon release of the actuating mem- 7. In an overload relay including a heating element and a switch normally yieldably urged to closed position, an actuating member operable tomove the switch to open position, means releasably securing the actuating member in fixed position, and a thermally actuated member adapted upon heating of the heating element to store up energy within itself to quickly move the actuating member to open the switch upon release of the actuating member, the thermally actuated member moving the actuating member to its inoperative;1 position after the occurrence of an overloa 8. In an overload relay having a heating element and ''a switch normally yieldably urged to closed position, an actuating mem ber operable to move the switch to open position, means releasably securing the actuating member in inactive position, and a thermally actuated member positioned in close thermal relation with the heating element to store up energy within itself upon heating of the heating element to quickly move the actuating member upon its release by an increase of temperature in its securing means to quickly open the switch, the thermally actuated member moving the actuating member to its inactive position to permit the switch to close before the actuating member is again secured in its inactive position.

9. A protective device of the character described comprising a switch biased to one osition, thermally actuated means normally iield in an inactive position and tending to move upon an increase in temperature thereat. to move the switch to another position, fusible means for holding the thermally actuated means inactive until the temperature at said fusible means reaches its fusion point, whereby energy is stored in said thermally actuated means to be released with a snap and impart a-corresponding quick movement to the switch, and heating means for the thermally actuated and fusible means, said thermally actuated means returning to a position permitting the switch to move to its first positionupon a recession of temperaturebefore the fusible means sets to hold the same inactive.

10. A protective device of the character described, comprising a switch biased to one position, a fixed heat conducting stem, a member journalled on said stem and adapted upon movement thereof to move the switch to another position, fusible means for securing the member against movement on the stem during all temperatures lower than the fusion point of said means, a heater in thermal relation to the stem, whereby heat is conducted to the fusible means by said stem, and a thermal element juxtaposed the heater for moving said journalled member about the stem to move the switch to said other position, said thermal element tending to move upon any change in temperature whereby it stores energy within itself as the heater raises the temperature at the fusible means which energy is released with a snap upon fusion of the fusible means to impart a corresponding quick movement to the switch.

11. A protective device of the character described, comprising; a switch biased to one position, a fixed heat conducting stem, a member journalled on said stem and adapted upon movement thereof to move the switch to another position, fusible means for securing thetemperatureto move the same and actuate the switch to said other position whereby energy is stored in said thermal element which is released with a snap to impart a corresponding movement to said journalled memfixed my hand.

' GUSTAV O. WILMS. 

